Electron microscopic histochemical methods will be developed and applied for the localization of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), acetylcholine, choline acetyltransferase, and cholinergic receptors. Neurotrophic factors essential for the maintenance of postsynaptic AChE will be investigated. The proposed role of AChe and BuChe will be investigated. The proposed role of BuChE as a precursor of AChE as an agent for the regulation of AChE will be examined.